Cartridge head space gaging device for rifle firing chambers



MaylZ, 1970 w. K. Dow 3,510,951

CARTRIDGE HEAD SPACE GAGING DEVICE FOR RIFLE FIRING CHAMBERS Filed Sept. 5, 1968 :ELQL LEI- ffl/lll LNVENTOR.

LUUHET KI! mu 3,510,951 CARTRIDGE HEAD SPACE GAGING DEVICE FOR RIFLE FIRING CHAMBERS Walter K. Dow, 86 Converse St., Longmeadow, Mass. 01106 Filed Sept. 3, 1968, Ser. No. 756,901 Int. Cl. G01b 5 00 U.S.; Cl. 33--143 9 Claims ABSTRACT OF THE DISCLOSURE A cartridge head space gaging device for rifle firing chambers having a tapered forward end. Front and rear gagemembers are slidably joined for relative axial movement and together duplicate significant portions of the outer configuration of a rifle cartridge shell surface from tapered fore end to rearend face. Frictional means resist relative sliding movement. The gage in over size lengthwise condition is inserted in a firing chamber, the rifle action closed and opened, and the gage removed for lengthwise measurement and comparison with an established maximum permissible length. Preferably a deformable ring of malleable material is placed between opposed faces of the members and is compressed when the rifle action is closed in order to provide a fixed mold to indicate the actual head space condition of the rifle.

This invention relates to new and useful improvements in devices for use in gaging or measuring the head space condition of a riiie firing chamber in which the chamber and cartridge shell therefor are provided with a tapered shoulder at the forward end. The device is particularly useful for small bore rifles and provides in its preferred form an accurate mold for measuring the space between the tapered forward shoulder of the firing chamber and the face of a breech block or bolt of a rifle in closed condition. By reference to such spacing it can be determined whether the head space of a rifle is within an acceptable maximum limit. The so-called head space is more accurately that amount of space between the forward end face of a rifle lbreech block or bolt,` when the riiie action is closed, and the head end of a cartridge when the cartridge is seated in the rifle firing chamber. In the event the cartridge head space of a riiie is excessive it is considered unsuitable for use from the` standpoint of the likelihood of faulty operation in firing the weapon and of possible injury to the person ring it.

DESCRIPTION `OF THE PRIOR ART Gages now commonly used for measuring the head space conditions of cartridge firing chambers of small bore rifles are generally of two types.

The first type is used primarily by the manufacturers of such firearms. It comprises a device having a tubular front member With an outer configuration duplicating theconfiguration at the forward end portion of a cartridge` shell having a tapered front end. A rear member is provided with a forwardly extending gaging stem fitting in the bore of the tubular front member. A heavy spring urges the members apart in an `axial direction against a fixed stop between the tubular member and the stem. In this condition an end face on the tip of the stem and an outer annular face at the tapered end of the tubular members are` in an exact co-planar relation. The length of the device in this condition is greater than the standard length of a cartridge. When this gage is seated in a rie firing chamberand the action closed, the breech block or bolt strikes the rear end of the rear member and will compress the spring to move the gaging stern forwardly of the UnitedStates Patent O tapered end of the tube. A gage indicator assembly is inserted through the front end of the barrel. The assembly has long stem probing members for contacting the end face of the gaging stem and annular face of the tubular member. Dial indicator readings are obtained which reflect the longitudinal displacement of the inner gaging stem relative to the outer tubular member and by such readings the head space" condition is ascertained.

The other type of head space gaging method is to provide a series of solid cartridge type plugs of various lengths. Plugs of increasing lengths are successively placed in the firing chamber of a rifle until the bolt refuses to close. By this go and no-go method, the head space condition is roughly calculated. Gages of this type are generally used in field testing. If the rifle receives an oversize plug the barrel is replaced.

An object of the present invention is to provide a device for the accurate measurement of head space conditions in small bore rifles which will disclose precise dimensions without the need for elaborate equipment.

A further object is to provide a cartridge head space gaging device for rifles having an extremely small bore which could not accept the indicator probing members of the first type of gage described above. This would apply to bores of less than seven or eight millimeters in diameter.

Another object is to provide a rie firing chamber head space gaging device which can be used as a permanent record of the initial head space in a recorded rifle chamber at the time of manufacture.

A still further object of the invention is to provide a head space gaging device for small bore weapons which will adjust to the actual head space of the chamber and provide an accurate mold of the head space conditions in a weapon of the type described.

Still another object of the invention is to provide a gaging device which in its preferred form includes a deformable member of malleable material which will serve as an impression of a metallic or plastic nature for preserving the record of the head space conditions.

SUMMARY OF THE INVENTION Devices embodying the present invention are charac terized by having a fore or front member shaped with an outer surface configuration including a tapered forward end which dimensionally conforms to the forward end of a cartridge shell for the chamber of a rifle, and a rear member provided with an end face engageable by the breech block or bolt of the rifle with outer portions forwardly thereof having outer surfaces identical with corresponding surfaces of the cartridge shell. The two members are joined together with a sliding fit for relative axial movement, one member preferably having an axial bore in which is received an elongated axial stem extension of the other member. Means for creating a frictional drag to axial movement between the members are also provided, and in a preferred embodiment the members have 0pposed shoulders between which a ring of malleable or plastic material may be inserted, the ring being permanently deformed in the use of the device.

In use the two members are separated and preferably by the deformable ring to define a length greater than the length of a standard cartridge shell for the rifle plus a maximum allowable head space. In such condition the device is inserted in the firing chamber. The action is closed, the breech bolt moving the two members together. After the action is opened and the device removed, a mold of a cartridge shell length plus head space is provided which may then be placed in any suitable measuring or gaging instrument to determine the exact dimension of the firing chamber as from the tapered fore end to the front face of the closed bolt. By reference to such measurement, the head space condition of a firing chamber may be ascertained precisely and corrective measures taken if needed. Furthermore, the malleable ring when deformed provides a means by which a precise and accurate mold condition can be duplicated even`though the two members may be axially shifted in removing the same from the chamber to the measuring instrument. i Other objects, features and advantages of the present invention will be apparent from the following description of several embodiments thereof as shown in the accompanying drawings. DRAWINGS FIG. 1 is a side elevation of a. preferred form of the gage device with parts in section, an open rifle firing chamber being diagrammatically indicated and the rear end of the device shown located in a position occupying more than a maximum allowable head space for the chamber;

FIG. 2 is a view similar to FIG. 1 diagrammatically indicating the rifle breech bolt in closed condition and the front face thereof having pushed the rear end of the device inwardly of the front end; and

FIGS. 3-7 are side elevations with parts in section of various modifications of the gage device seen in FIGS. 1 and 2.

In FIGS. 1 and 2 the breech end of a rie barrel is represented with the cylindrical portion of a ring chamber at 2, an inwardly tapered or shouldered fore portion at 4, and the bore of the barrel at 6. In FIG. l a gage device embodying the invention is shown in seated relation in chamber 2 against taper 4 and represents the condition of the device relative to the chamber prior to closing the action of the rie. In FIG. 2 the condition of the device is shown after closing the action as by locking the bolt or breech block. In the latter condition the dimensional conditions under which a live cartridge would be fired are duplicated, the fore end of a bolt being indicated at S in FIG. 2. As will be noted the front face of the bolt engages the rear end of the device and pushes a rear member of the device forward relative to a front member.

The rear member 12 and front member 14 of the device are slidably joined together for relative longitudinal or axial movement. The external surface configuration of the two members when fitted together, as in FIGS. 1 and 2, is substantially identical dimensionally (except lengthwise) to that of the external conguration of actual cartridge shells of cartridges suitable for tiring in the rifle chamber 2. The surface configuration of the device of FIGS. 1 and 2 and the modified devices of FIGS. 4, 6` and 7 is similar to that of cartridge shells used in the well known M-16 military rifle. The configuration of the modifications of FIGS. 3 and 5 simulates the configuration of field service head space plug gages (as described above) for the same weapon, the rear end of the latter devices being relieved to avoid contact with the ejector pin of the weapon as will be appreciated by those familiar with this type of gage.

Relative axial movement between members 12 and 14 is provided by an axial through bore 16 in member 12 in which an elongated axially extending stem 18 of member 14 is received. Stem 18 has a precision sliding tit in the bore 16. It may further be provided with a series of annular grooves 20` in which are mounted rings 22 of frictional material such as neoprene or rubber. Thus a desired degree of resistance may be provided against unintentional sliding movement between the two -members when the device is being used to check head space measurements.

Moreover, in the preferred form of device a ring 24 of malleable metallic material such as lead composition, or suitable deformable plastic composition, surrounds stem 18 against the annular shoulder 26 of the front member 14. The opposing annular end face 28 of member 12 surrounding stem 18 may abut ring 24 and in such condition holds the two members apart dening a length from front to rear slightly in excess of the standard cartridge shell length plus the predetermined maximum -allowable head space-for a particular weapon chamber. Accordingly, as seated in chamber 12 (FIG. 1) the end face 30 of the device will be disposed rearwardly of the chamber opening at a location which (if xed at such location) would normally prevent the breech bolt from locking into closed position for tiring the gun under conditions where the cartridge head space of the rie is within acceptable maximum limits.

In the event the rifle action were to be closed without disturbing the relation of the parts of the device as shown by FIG. 1, removal of the device and checking the length thereof in a suitable measuring instrument would immediately disclose the fact that the head space condition'was unsatisfactory. Corrective measures could then be taken to adjust the head space. In the case of a manufacturer this could mean alterations in the mounting of the barrel, adjustment of receiver parts, or replacing the barrel. In the case of a field inspection normally the barrel would be replaced on the assumption that continued firing of the ritievhad worn or enlarged the chamber to create an excessive head space dimension.

Where, as is most commonly the result of closing the bolt 8, the rear member 12 does move forwardly relative to front member 14 (as shown in somewhat exaggerated form by FIG. 2) the ring 24 is squeezed and deformed between the opposed shoulder portions 26 and 28. The device is then removed from the chamber, suitably checked for length against the predetermined maximum allowance dimension to reveal the head space condition, and if needed the adjustments as above described may then be made.

It may be noted that where a soft metal ring is used and deformed as illustrated, the parts 12 and 14 may be moved relative to each other by subsequent handling and yet the original compressed condition of the gage be reproduced by retaining the crushed ring on stem 18. Thus, if desired, a simple mold of the chamber can be preserved and serve as a permanent record of the initial (or subsequent) head space condition in a registered rie. This may be used for any recording purposes as for comparison purposes after a given series of rings of a weapon so to determine the wear or expansion characterisrtics of the chamber in a particular type of rie.

Where the head space condition of a rie chamber is checked simply for determining the suitability of the weapon for continued use the deformed ring 24 may be removed from stem 18 and another ring of a similar regulated diameter inserted between anged shoulders 26 and 28 for checking the chamber of another rie.

It is to be noted that the degree of resistance provided by the friction rings 22 may be minimal where a deformable ring 24 is employed. This is for the reason that ring 24 permits the later duplication for measuring purposes of the actual head space conditions whether or not any relative axial movement has meanwhile taken place between the front and rear members of the device.

The deformable ring 24 may, however, be unnecessary l where the gage device is simply used for successively checking a series of Weapons. In such case a degree of frictional resistance may be provided by friction rings 22 in order to prevent any unintentional or inadvertent relative movement between the front and rear members when removing the device from a chamber and transferring it to a measuring instrument for checking the length. In using the device without the ring the parts may be manually opened up' in length to a degree dening an oversize condition and inserted in the chamber, the action then locked in closed condition and opened, and the device subsequently removed for measuring. The friction rings 22 provide not only resistance to overrunning when the bolt is moved to close the rifle action but also to any separation lengthwise when removing the device and placing it in the measuring gage.

,This.,frictiona1`resistance, indevices embodying the inventionyleither with or wthout the use of deformable fingsfmayl be'applied in'va'rious ways and various modifications `may be also made in'the'particular construction ofthe slidably engaged parts.` Several examples are illustrated by FIGS. 3 to 7 inclusive.`

In FIG. 3 ,a front member 30 with tapered fore end is provided with a through boreV 31I receiving a stern 32 of the rear member 34. Stem `32"is provided with friction rings 35 similar to the rings`22y of'FIGS. l and 2.l The bod'portion' for slidably fitting `in a cartridge chamber` is providedwith a relievedrear end portion at 37 for avoiding contactwith the ejector pin as above mentioned. It will also be noted that ftp/,deformable ring 38 is disposed against the shouldered portion of the body 36 adjacent the rear of the device.

In `FIG..4 front member 40 is provided with a stem extension 4h and is shouldered centrally of the device fori insertion of the deformable ring 42 at this location. The frictional means in this modification is provided by `set screws as at 44 `threaded in the body of rear member 45 in radial relation to the stem 41. The set screws are formed with tips 45 of plastic frictional materialisuch as a suitable nylon formulation for bearing against the surface of stem 41. The set screws 44 `can `be adjusted to increase or decrease the friction as desirable.

In FIG. the construction varies from that of FIG. 3 in providing a shouldered bore 50 in the front member 51 and in providing a frictional means for resisting relative movement in the form of an elongated inlay piece 52 lof frictional material, as neopene or similar plastic material, fitted in a recessed surface of stem 54 of the rear mmeber` S5.

In FIGS. 6 and 7 the opposing shouldered portions of the `front and rear members, between which deformable rings (as at 60 and 70, respectively) are located, are disposed centrally of the devices shown. In FIG. 6 a plug 611` of neoprene or similar material is seated in a central hollow portion of stern l62 and may be expanded by a set screw 63 threaded in the outer section of the hollowed stem. As noted, the annular wall of stem 62 surrounding the plug and set screw is relatively thin and may thus be expanded sufficiently to provide varying degrees of resistance to sliding` movement in the bore 64 of the rear member. In FIG. 7 a tapered hole 71 is formed in the er1-d of stem 72. Threaded in hole 71 is a tapered set screw 73"which may be turned to expand the end portion of the stem. Thus the set screw may vary the frictional fit of stem 72" in the bore 74 of the rear member in this form ofthe device.

It will beunderstood that other changes may be made inthe details of construction and arrangement of parts without departing from the scope of the invention as expressed in the accompanying claims. I therefore do not wish to be limited to the exact details of construction and arrangement of parts as shown and described `by way of illustration i only.

What is claimed is: p

1. A gage device for determining the cartridge head space condition of a rifle having a firing chamber with a tapered shoulder at the forward end thereof, comprising: frontiand rear members having slidably engaged portionsfor relative axial movement between the members, said members also having longitudinally opposed surfaces and a deformable means disposed between said surfaces, the front member at its fore end having outer surface configurations substantially identical dimensionally with the forwardly tapered portion of a rie cartridge` shell for said firing chamber and with portions of said shell rearwardly adjacent said tapered portion,

the rear member having an end face for engagement by the breech block of a rifle and a section forwardly of said end face being provided with an outer surface configuration substantially identical dimensionally with a section of the said rife cartridge shell forwardly of the rear end thereof, and

means for frictionally resisting .free sliding movement between said members,

said deformable means in a position of engagement between said opposed surfaces holding said members in a condition of longitudinal separation in which the gage length is greater than the standard length of a tie cartridge shell from the tapered portion to the rear end face Vthereof plus a maximum allowable head space,

whereby said gage device may be inserted in a firing chamber, the breech block of the rifle closed and opened, and the gage thereafter removed with said deformable means compressed for measuring the length thereof as established by the closing of said breech block.

2. A gage device for determining the cartridge head space condition of a bolt action rifle having a firing chamber with a tapered shoulder at the forward end thereof, comprising:

separable front and rear members having slidably engageable portions enabling relative axial movement between the members,

said members further having longitudinally opposed annular surfaces and a deformable member disposed between said surfaces,

means carried by one of said slidable portions for frictionally resisting said relative axial movement,

said members having outer surface configurations simulating the outer surface configurations of a rifle cartridge shell at the forward tapered end of the shell and at the rear end thereof, and

said members when held in longitudinally separated condition by said deformable member in contact with said opposed surfaces defining a length greater than the standard length of a cartridge shell plus a maximum allowable head space for insertion of the device into a rifle firing chamber and closing the bolt thereof whereby said members are moved together compressing said deformable member for subsequent removal of the device and measurement thereof to ascertain the spacing between the tapered shoulder of the firing chamber and the face of the bolt when the action of the rifle is closed.

3. The structure of claim 2 in which:

said deformable member between said surfaces is annular in form and surrounds one of said separable members.

4. The structure of claim 3 in which:

said slidably engageable portions are formed by an axially extending stem of one of said members and an axial bore in the other member receiving said stem,

a shoulder at the inner end of the stem and the annular end face of said other member form said longitudinally opposed surfaces, and

said deformable member is a ring of malleable material surrounding said stem.

5. The structure of claim 4 in which:

said ring of malleable material is slidably mounted on said stem.

6. The structure of claim 5 in which:

said means frictionally resisting relative sliding movement between said members comprises a series of rings of frictional material disposed in longitudinally spaced circumferential grooves of said stem.

7. The structure of claim 5 in which:

said means frictionally resisting relative sliding movement between said members comprises radially directed set screws in said stem receiving member having frictional material at the inner ends intersecting said bore and engaging the surface of said a tapered hollow portion in the outer end of said axial stem. stem and a tapered set screw threaded therein to ad- 8. The structure of claim 5, in which: just the sliding t of the outer end portion of the said means frictionally resisting relative sliding movestemin said axial bore.

ment between said members comprises 5 a hollowed portion in said axially extending stem in References Cited which a plug of expandable material is seated, and a set screw is threaded in the entrance end of the hol- UNITED STATES PATENTS lowed portion against the plug for compressing the 2,363,165 11/ 1944 Vierling.

same and expanding the stem to adjust the sliding 10 2,649,782 8/1953 Smith.

t 0f the Stem in Said axialbore- 2,544,158 3/1951 Henderson 33 143 9. The structure of claim S, in which:

said means frictionally resisting relative sliding move- SAMUEL S. MATTHEWS, Primary Examiner ment between said members comprises 

